Wear bushing for underwater drilling apparatus



Aug. 5, 1969 F. J. SCHUH WEAR BUSHING FOR UNDERWATER DRILLING APPARATUS Filed March 8, 1967 I NVEN TOR. neg/we J. SCI/UH 4 r Tom/EX United States Patent Ofice 3,459,270 WEAR BUSHING FOR UNDERWATER DRILLING APPARATUS Frank J. Schuh, Dallas, Tex., assignor to Atlantic Richfield Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 8, 1967, Ser. No. 621,484 Int. Cl. E21b /02, 33/03 US. Cl. 175-7 3 Claims ABSTRACT OF THE DISCLOSURE This application relates to a wear bushing for use proximate the upper end of a blowout preventer assembly in an ocean floor drilling apparatus to protect the internal surfaces of the blowout preventer assembly from the lateral contact forces of the drill pipe which are present when the riser, which extends from a floating vessel, is not perfectly aligned with the blowout preventer assembly.

My present invention relates to offshore drilling, and more particularly relates to a wear bushing for preventing internal damage to a blowout preventer assembly mounted on a formation underlying a body of water when drilling is conducted through the blowout preventer assembly with a drill string operated from a vessel floating on the body of water.

It has been proposed in the prior art that bit guides or other protective means be provided in well head equipment to protect machined sealing surfaces therein from damage which may be caused by contact with drilling tools lowered through the well head. In relatively deep water, drilling through a well head positioned on an ocean floor with a drill string rotated from a vessel floating on the ocean and wherein the vessel is laterally misaligned with respect to the well head, results in the drill string wearing or cutting laterally into the inner side surfaces of the blowout preventer equipment and frequently causes failure in the blowout preventer equipment. This wear problem results from the high lateral contact force of the drill pipe on the blowout preventers and is particularly severe in areas where strong currents are encountered, such as the Cook Inlet of Alaska where the casing riser, extending between the vessel and blowout preventer assembly, is not perfectly aligned with the 'blowout preventer assembly. It is this lateral force, combined with the rotation of the drill string during the drilling operation and the vertical movement of the drill string while round tripping the drill bit, which cause excessive wear in the blowout preventers. The blowout preventer internal wear problem is particularly pronounced where there is a reduction in bore size from the riser to the blowout preventer.

Accordingly, it is an object of the present invention to provide wear protection means above the blowout preventer assembly for preventing excessive wear in the blowout preventers.

It is also an object of my present invention to provide a wear bushing which can be readily installed with a drill pipe on top of the blowout preventer assembly mounted on the ocean floor, from a vessel floating on the ocean.

A further object of my present invention is to provide a support means for a wear bushing for protecting a blowout preventer assembly mounted on the ocean floor.

Other objects and a more complete understanding of my present invention will become apparent from the following specification and the appended claims when considered in conjunction with the drawings, wherein:

FIG. 1 shows a blowout preventer assembly mounted 3,459,270 Patented Aug. 5, 1969 on an ocean floor drilling head during a drilling operation contemplated in my present invention; and

FIG. 2 shows an enlarged view of a wear bushing during its installation in operative position proximate the lower end of a riser assembly.

Referring now generally to the drawings, a wear bushing 10 is installed in a lateral flex or ball joint 12 and is of a size to permit the wear bushing 10 to seat in the bottom section 14 of a ball joint 12 at the lower end of riser assembly 46. As best shown in FIG. 2, the wear bushing 10 may be installed inoperative position by carrying the wear bushing in on the drill bit 16 or a drill collar 18, either of which may provide a shoulder surface to support the wear bushing at its outwardly tapering face 20.

Referring now more particularly to FIG. 1, a well head 22 is installed on the ocean floor 24 and consists of a landing base 26, a conductor pipe 28, and casings 30 and 32 hung in the well head and cemented to the formation in accordance with conventional practice. Above the well base 26 is a guide frame 34 with guide lines 36 extending to the drilling vessel above and used for guiding equipment from the vessel to the ocean floor as with a guide arm 38 which is slideably attached to the guide lines 36. The blowout preventer assembly or stack consists of a number of blowout preventers, typically a double Shafer blowout preventer 40, a Hydril 42 and a connector 44 for connecting the upper end of the blowout preventer assembly to the lower end of the riser 46. A ball joint 12 is provided at the lower end of the riser 46 to provide lateral flexibility in the riser pipe.

As shown in FIG. 2, the lower member 14 of the ball joint 12 is of a smaller diameter or bore than the upper member 13 since the internal diameter of the blowout preventer equipment as shown schematically by the phantom lines 48 in FIG. 1, is less than the internal diameter of the riser 46. Hence, the restriction formed by the lower member 14 of the ball joint 12 provides a shoulder 50 or a seat. In my present invention, I advantageously use this seat 50 to support the wear bushing 10 which has an outwardly flared surface 52 or any other convenient shoulder means which seats on the shoulder surface 50 of the ball joint.

The wear busing 10 has an internal bore 54 large enough to receive the drill string 56, but the bushing 10 will not fit over the drill collar 18 or the drill bit 16 if no collars are used, and hence, the bushing can be carried in through the riser and onto its supporting surface 50 as the drill bit 16 is lowered from the vessel (not shown) through the blowout preventer equipment and into the formation. When the drill string 56 is lowered to the point where the wear bushing 10, carried on the drill bit, passes into the lower member 14 of the ball joint so that the external shoulder 52 of the wear bushing engages the seat 50 formed in the ball joint lower member, the wear bushing 10 is in place to serve its function to protect the blowout preventer equipment. As can be seen in the drawings, the wear bushing 10 centralizes the drill string 56- so that it cannot laterally contact the internal surfaces of the blowout preventer equipment. The wear bushing also provided an inexpensive and easily replaceable preferential wear surface.

The wear bushing 10 is installed and retrieved through the riser 46 on the drill string 56 each time the drill bit 16 is brought to the vessel. After the drill bit has been dulled, the drill string is pulled and as the bit passes upwardly through the blowout preventer equipment it engages the lower surface 20 of the Wear bushing and pulls the wear bushing to the vessel. Hence, each time the bit is changed, the wear bushing is raised to the surface where it can be inspected and replaced if necessary before running the new drill bit.

The wear bushing of my present invention may also have an internal diameter larger than the drill bit or collars, in which case, the wear bushing may be installed with a special running and retrieving tool on a drill pipe and would remain in place during drill bit changes and until it was desired to inspect or replace the wear bushing.

Although my present invention has been described herein with respect to a specific embodiment, it is to be understood that my invention is not limited to the details set forth but should be afforded to full scope of the appending claims.

I claim:

1. Apparatus for underwater drilling wherein a drill string is oeprated from a floating vessel through a riser assembly extending from said vessel through a body of water to a blowout preventer assembly mounted on a formation underlying said body of water, comprising in combination:

a wear bushing installed proximate the upper end of said blowout preventer assembly to centralize said drill string in said blowout preventer assembly during rotation thereof through said assemblies to make a hole in said formation, and thereby prevent contact between said drill string and the internal surfaces of said blowout preventer assembly, and

a ball joint positioned proximate the lower end of said riser, said ball joint having a lower member of reduced internal diameter, said lower member forming a seat at said reduced diameter, and said wear bushing having an external shoulder adapted to rest on said ball joint seat.

2. The apparatus of claim 1 wherein said wear bushing has a lower shoulder for engaging an enlargement on the lower end of the drill string to thereby support said wear bushing on said drill string until the external shoulder of said bushing engages said ball joint seat as said drill string is lowered through said riser and into said blowout preventer assembly.

3. Apparatus for underwater drilling wherein a drill string is operated from a floating vessel through a riser assembly extending from said vessel through a body of water to a blowout preventer assembly mounted on a formation underlying said body of water, comprising in combination:

a wear bushing installed in the lower end of said riser proximate the upper end of said blowout preventer assembly to centralize said drill string in said blowout preventer assembly during rotation thereof through said assemblies to make a hole in said formation, and thereby prevent contact between said drill string and the internal surfaces of said blowout preventer assembly, and

a shoulder means in said riser proximate the lower end thereof, forming a seat for said bushing, said bushing having an external shoulder adapted to rest on said riser shoulder seat.

References Cited UNITED STATES PATENTS 2,808,229 10/1957 Bauer et al 166-88 2,995,196 8/1961 Gibson et al. -7 3,247,914 4/1966 Slack 166-.5 3,227,229 1/1966 Wakefield 175-7 3,324,943 6/1967 Price 175-7 JAMES A. LEPPINK, Primary Examiner U.S. Cl. X.R. 166-75 

